The present invention relates to a hermetically sealing apparatus which is adapted to seal two members which rotate relative to each other.
Conventionally, for instance, an apparatus shown in FIG. 3 is known as a hermetically sealing apparatus of this type. In this conventional example, the hermetically sealing apparatus is provided with a first seal ring having a seal lip 100 made of a rubber-like resilient material, a tip 102 of the seal lip 100 abuts against a rotating shaft, thereby constituting a first seal portion. The hermetically sealing apparatus is further provided with a second seal ring having a seal lip 103 made of a resin and extending along a side surface of the first seal ring on the atmosphere side, and a tip 104 of the seal lip 103 abuts against the rotating shaft, thereby constituting a second seal portion. The seal lip 100 made of the rubber-like resilient material is backed up by the seal lip 103 which has a low level of frictional resistance so as to restrain an increase in the contact surface pressure of a hermetic fluid under high pressure, thereby restraining an increase in sliding resistance between the seal lip 100 and the rotating shaft. This arrangement makes it possible to reduce the abrasion of the seal lip 100 and improve the durability thereof. The second seal ring is held by a backup ring 105. In order to fabricate such a hermetically sealing apparatus, the following procedure is generally taken: Using a rubber-like resilient material, the seal lip 100 is obtained by a process of forming the seal lip 100 by vulcanization. The resin-made seal lip 104 is obtained by subjecting a resin-made seal lip to a bending process. The, these seal lips 100 and 104 are superposed on the metallic reinforcing ring 105 and are fixed to each other by bonding with an adhesive or by calking a metallic outer ring 106, securing the ends of the superposed members.
However, in accordance with the arrangement of such a conventional example described above, since the affinity between the resin and rubber is poor and it is impossible to obtain a sufficient bonding force, it is necessary to provide a process in which the joint surface of the resin-made seal lip on the rubber-like seal lip side is preliminarily processed by means of metal sodium or the like for good fitting to the adhesive before jointing is effected. When securing by calking is effected, it is necessary to use the metallic outer ring, so that the number of parts disadvantageously increases. Accordingly, in cases where either of the fixing methods is used, the number of processes involved until completion of the hermetically sealing apparatus becomes undesirably numerous. Hence, there has been a drawback in that the production cost is high.